<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>学习到的小技巧</title>
</head>

<body>
    <!-- 如果前面不写标签名，则默认为 div -->
    <!-- p.aaa + enter -->
    <p class="aaa"></p>
    <!-- .aaa + enter -->
    <div class="aaa"></div>
    <!-- span.aaa + enter -->
    <span class="aaa"></span>
    <!-- a.aaa + enter-->
    <a href="" class="aaa"></a>

    <!-- #bbb + enter => 不起效果 -->
    <!-- div#bbb + enter -->
    <div id="bbb"></div>
    <!-- a#bbb + enter -->
    <a href="" id="bbb"></a>
    <!-- p#bbb + enter -->
    <p id="bbb"></p>
    <!-- span#bbb + enter -->
    <span id="bbb"></span>

</body>

</html>